1. Field of the Invention
The present invention generally relates to the field of fiber production, such as superfine fibers of micron and sub-micron size diameters as well as nanofibers. Superfine fibers may be made of a variety of materials.
2. Description of Related Art
Fibers having small diameters (e.g., micrometer (“micron”) to nanometer (“nano”)) are useful in a variety of fields from clothing industry to military applications. For example, in the biomedical field, there is a strong interest in developing structures based on nanofibers that provide a scaffolding for tissue growth to effectively support living cells. In the textile field, there is a strong interest in nanofibers because the nanofibers have a high surface area per unit mass that provide light but highly wear-resistant garments. As a class, carbon nanofibers are being used, for example, in reinforced composites, in heat management, and in reinforcement of elastomers. Many potential applications for small-diameter fibers are being developed as the ability to manufacture and control their chemical and physical properties improves.
It is well known in fiber manufacturing to produce extremely fine fibrous materials of organic fibers, such as described in U.S. Pat. Nos. 4,043,331 and 4,044,404, where a fibrillar mat product is prepared by electrostatically spinning an organic material and subsequently collecting spun fibers on a suitable surface; U.S. Pat. No. 4,266,918, where a controlled pressure is applied to a molten polymer which is emitted through an opening of an energy charged plate; and U.S. Pat. No. 4,323,525, where a water soluble polymer is fed by a series of spaced syringes into an electric field including an energy charged metal mandrel having a sheath of aluminum foil wrapper therearound which may be coated with a PTFE (Teflon™) release agent. Attention is further directed to U.S. Pat. Nos. 4,044,404, 4,639,390, 4,657,743, 4,842,505, 5,522,879, 6,106,913 and 6,111,590 . . . all of which feature polymer nanofiber production arrangements.
Electrospinning is a major manufacturing method to make nanofibers. Examples of methods and machinery used for electrospinning can be found, for example, in the following U.S. Pat. Nos. 6,616,435; 6,713,011; 7,083,854; and 7,134,857.